Carburetor



Dec. 14, 1965 Filed Oct.

FIG

w. B. SHEPHERD, JR 3,223,391

CARBURETOR 3 SheetS Sheet 2 INVENTOP 4 (I) \Dmanaz B. $HEVHERD, JR.

w/Ml 74m ATTO EN EYS Dec. 14, 1965 w. B. SHEPHERDFJR 3,223,391

CARBURETOR Filed Oct. 26, 1962 3 Sheets-Sheet 5 QT TO ZN'EYS 3O m.p.h.with no load or acceleration demands.

United States Patent 3,223,391 CARBURETOR Warner B. Shepherd, Jr., 831th St., Verona, Pa. Filed Oct. 26, 1962, Ser. No. 233,261 2 Claims. (Cl.261-23) This invention relates to improved carburetors.

In conventional automotive carburation systems, fuel is Supplied tocombustion chambers of an internal combustion engine by means ofmetering jets which feed fuel to the engine via the intake manifoldthereof in proportion to venturi action caused by air being drawnthrough ventun'es or responsive to manifold pressure.

Conventional carburetors, as, for example, a standard multiple barrelcarburetor employed primary jets as the only supply of fuel at cruisingspeeds below approximately Under load conditions, such as when thevehicle employing the carburetor is accelerating or climbing hills,additional fuel is supplied to the engine by a power jet normallyactuated by manifold vacuum or pressure. In some cases, this powered jetis a separate jet from the primary jets, and, in other cases, includesmeans for increasing the effective size of the primary jet or jets. At apredetermined high speed of approximately 45 m.p.h. or over, and formaximum power demands, still another supply of fuel is furnished bysecondary jet means which are normally located in separate speed throatsof the carburetor. The secondary jet means are normally inoperative atlow speeds whereby they close the high speed throats of the carburetor.The secondary jet means are usually operated by a combination ofmanifold vacuum and venturi action in the low speed throats of thecarburetor. Each of the aforementioned jet or jet systems are designedto give the proper fuel-air ratio necessary to properly operate theengine under all speed, power and acceleration requirements. With allthe above mentioned jets in operation at a speed of, for example, 65m.p.h. at full load requirements, the jets are effecting a maximumsupply of fuel which mixes with the amount of air being drawn in at thatspeed to provide a relatively rich fuel-air ratio. If the speed of thevehicle is then increased to approximately 90 m.p.h. with the throttlewide open or substantially wide open, the carburetor is supplying asubstantially leaner mixture to the engine than at 65 m.p.h. This isbecause at wide open throttle, air is being drawn in at a rapid ratewith very little restriction or friction while the rapid flow of fuelthrough the jets is highly restricted thereby causing an increasedamount of friction which obviously retards the flow of fuel. Conversely,at intermediate speeds of say 55 m.p.h., the fuel-air ratio is at amaximum because the fiow of air through the carburetor is quiterestricted while the fuel jets are not. This results in the fuel-airmixture being richer than necessary at cruising speeds thereby burningan excess amount of fuel and causing the fuel-air mixture to be quitelean at very high cruising speeds which reduces the maximum power outputof the engine and often results in damage to the engine such, forexample, as burning of the exhaust valves. At wide open throttle andhigh speeds it is desirable that the engine develop maximum poweroutput, particularly when the engine is used for racing purposes.

It is well known that maximum power of an internal combustion engine isproduced when the fuel-air mixture supplied thereto is relativelyl rich.Also, it is well known that relatively lean mixtures, particularly athigh speeds and wide open throttle, may damage the parts of an internalcombustion engine due to, for example, the burning of the exhaust valvesof the engine, excessive pre-ignition of the fuel, etc. It is alsodesirable to have the fuel-air mixture supplied to an internalcombustion engine at normal cruising speeds, to be relatively lean formaximum economy. However, in conventional carburetors, it is necessarythat the fuel-air mixture at normal cruising speeds, be relatively richin order that the jets of the carburetor may supply sufficient fuel atvery high engine speeds.

Accordingly, it is a primary object of this invention to provide new andimproved means for a carburetor, whereby the fuel to air ratio suppliedby the carburetor is automatically properly regulated throughout thefull range of engine speeds, whereby the fuel-air mixture is relativelylean at normal cruising speeds for maximum economy and is relativelyrich at very high speeds for maximum power and engine protection.

It is still another object of this invention to provide a new and novelcarburetion system effective to greatly increase the economy of engineoperation by maintaining the fuel to air ratio supplied by thecarburetion system at the proper ratio regardless of the speeds ofengine operation.

It is still another object of this invention to provide a new and novelmeans whereby standard carburetors may be modified inexpensively with aminimum of conversion operations to effect a regulated carburetioncontrol of engines through all speed ranges, and more particularly atextreme high engine speeds, at which improper carburetion control wouldcause serious damage to the engine and prevent the engine from producingits maximum power output.

These, together with other objects and advantages which will becomesubsequently apparent, reside in the details of construction andoperation as more fully hereinafter described and claimed, referencebeing had to the accompanying drawings forming a part thereof, whereinlike reference numerals refer to like parts throughout and in which:

FIG. 1 is a perspective view of a conventional four barrel carburetormodified .in accordance with the invention disclosed herein;

FIG. 2 is a diagrammatic view of the jets employed in the carburetorshown in FIG. 1;

FIG. 3 is an enlarged elevational view of the carburetor shown in FIG.1, with portions broken away so as to show the main metering system;

FIG. 4 is an enlarged elevational view of the carburetor shown in FIG. 1with portions broken away so as to show the idling metering system andmy improved high speed metering system;

FIG. 5 is a view similar to FIG. 4, but showing the power enrichmentsystem;

FIG. 6 is a View similar to FIGS. 4 and 5, but showing the secondarymetering system;

FIG. 7 is a perspective view of the top of the carburetor in an invertedposition;

FIG. 8 is an enlarged vertical cross sectional View taken through themetering jets for the high speed metering system shown in FIG. 7.

The invention is illustrated in the drawings as applied to a carburetorsimilar to the Holley Carburetor Model 4000 for 1955 and 1956 Fords,Lincolns, and Mercurys. However, it is to be understood that theinvention could be applied to similar carburetors of a diiferent makeand model.

As illustrated in FIG. 4, the carburetor 10 includes a top 12, a mainbody 14, and a throttle assembly 16.

The main body 14 includes a conventional float chamber 18 containing aconventional inlet valve operated by a float in the float chamber 18,not shown. The float operated valve is connected by conduit means to thefuel pump of the vehicle engine.

The throttle assembly 16 includes a throttle housing 20 provided withtwo vertically extending parallel primary throttle passages 22 and 24and two vertically extending parallel secondary or high speed throttlepassages 26 and 28. A horizontal throttle shaft 30 extends diametricallythrough the housing and through the primary throttle passages 22 and 24,and a secondary throttle shaft 32 extends parallel to the shaft throughthe secondary throttle passages 26 and 28. The throttle shafts 30 and 32each have secured thereto a pair of substantially circular throttleplates 34 and 36 respectively in the primary and secondary passages. Thethrottle shaft 30 is connected to a conventional accelerator pedal bymeans of a conventional linkage, not shown, and the throttle shaft 32 asshown in FIG. 6, is connected to a pneumatic motor 38. The housing ofthe motor 38 is divided into an atmospheric chamber 40 and a vacuumchamber 42 by flexible diaphragm 44. The diaphragm 44 is operativelyconnected to the shaft 32 by means of a plate 45 secured to the shaftand a rod 46 pivotally connected at one end by means of a pin 48 to theplate and abutting the diaphragm at its other end by means of a thrustplate 50 which may be secured to the diaphragm. A coil spring 52 iscompressed between one wall of the motor housing and the diaphragm so asto urge the throttle plates 36 to a closed position.

The upper ends of the primary passages 22 and 24 and the secondarypassages 26 and 28 are restricted so as to form venturi passages 54 inthe primary passages and venturi passages 56 in the secondary or highspeed passages. As shown in FIGS. 1 and 4, the upper ends of theventuries 56 are each formed with a flared inlet opening 58 and theventuries 54 in the primary throttle passages communicate with laterallyextending passages 60 formed through one side wall of the main body 14.A pair of choke plates 62 in passages 60 are mounted on a choke shaft64. The choke shaft 64 has one end connected to a conventionalthermostatic operator which normally maintains the choke plates 62 in aclosed position as illustrated in FIG. 1. After the intake manifold ofthe engine has been properly heated, the thermostatic operator rotatesthe shaft 64 and choke plates 62 to the open position illustrated inFIG. 4.

When the accelerator pedal controlling the carburetor is released, thetwo primary throttle plates 34 are urged by spring means, not shown, tothe closed position as illustrated in FIG. 4. Atmospheric pressureacting on the fuel in the float chamber 18 forces the fuel to flowthrough a main jet 66 into a main well 68. From the main well 68, thefuel flows upwardly through an idling well 70, then horizontally throughan idle restriction 72 and downwardly through an idle passagerestriction 74 into a vertical passage 76 which terminates in ahorizontally extending chamber 78. As the fuel flows through the idlerestriction 72 it is mixed with air passing through an idle bleed 80.This bleed also acts as a vent to prevent any siphoning effect throughthe idle system at high speeds or when the engine is stopped. As thefuel flows from the chamber 78 into the passage 82, additional airenters the chamber 78 through the two idler transfer holes 84 and ismixed with the fuel. The fuel and air mixture then flows past theadjustable idler needle valve 86 which controls the mixture delivered atidle. From the idle adjusting needle chamber 88, the fuel-air mixturethen flows downwardly through a short diagonal passage to a horizontallyextneding groove 90 in the bottom surface of the throttle assembly 16.The groove 90 leads to a point midway between the passages 22 and 26 toa plurality of branches whereby the fuel mixture is discharged into boththe primary and secondary passages 22 and 26 thereby ensuring an evendistribution of fuel throughout the manifold at idle. An identical idlesystem is also provided for the primary and secondary passages 24 and28. When the throttle plate 34 is slightly opened, fuel also begins toflow through the idle transfer holes 84 as they are exposed to manifoldvacuum.

As the throttle plate is opened still wider and the engine speedincreases, the air flow through the carburetor is also increased. Thiscreates a vacuum in the venturi passages 54 strong enough to bring themain metering system shown in FIG. 3, into operation. The flow from theidle system tapers off as the main metering system begins dischargingfuel whereby the two systems provide a smooth and gradual transitionfrom idle to cruising speeds. In the area of the greatest vacuum in thethroat of the primary venturi 54, a small boost venturi 92 is located. Avacuum is created within this smaller venturi which is stronger thanthat in the primary venturi 54, but still proportional to the air flowthrough the carburetor. This difference in pressure between the vacuumin the boost venturi and the normal air pressure in the float chamber 18causes fuel to flow through the main metering system provided for eachof the primary throttle passages 22 and 24, one of which is illustratedin FIG. 3. At cruising speeds of approximately 30 mph or greater, thefuel flows from the fioat chamber 18 through the main jets 66 into thebottom of the main well 68. The fuel moves up the main well 68 throughthe main well tube 94 where air is spread into the fuel by small passage96 extending radially through the side of the main well tubes andvertical-1y upwardly adjacent one side thereof. This mixture of fuel andair, being lighter than raw fuel, responds faster to any change inventuri vacuum and vaporizes more readily than raw fuel when dischargedinto the air stream of the venturi. As the fuel ejects from theaspirating nozzle 97 of the main well tube, additional air is mixedtherewith by means of a vent 98 in the top 12. This mixture of fuel andair then moves downwardly through a passage 100 whereby it is dischargedinto the throat of the boost venturi 92 by means of a nozzle 102. Thethrottle plate 34 controls the amount of fuel-air mixture admitted tothe intake manifold, thereby regulating the speed and power output ofthe engine in accordance with accelerator pedal movement. There areidentical main metering systems in both primary passages 22 and 24.

A transfer tube 104 is mounted adjacent the bottom edge of each boostventuri 92 whereby any excess fuel collecting on the boost venturi issucked into the transfer tube and through a vertical passage 106 wherebythe fuel is ejected into the intake manifold by means of the groove 90.The transfer tube is particularly effective during idling to withdrawany excess fuel on the boost venturi.

During high power operations, particularly at lower engine speeds, suchas during acceleration, the carburetor must deliver a richer mixturethan is needed when the engine is running at cruisng speed with no greatpower output required. The added fuel for efficient operation issupplied by the power enrichment system shown in FIG. 5 and sometimesreferred to as the economizer system.

The power enrichment system is controlled by manifold vacuum, whichgives an accurate indication of the power demands placed upon theengine. Manifold vacuum is strongest at idle and decreases as the loadon the engine is increased. As the load on the engine is increased, thethrottle plates must be opened wider to maintain any given speed.Manifold vacuum is reduced because the opened throttle plates ofier lessrestriction to air entering the intake manifold.

Manifold vacuum from below the primary throttle plates 34 is transmittedthrough a vacuum passage 108 in the throttle assembly 16, the main body14 and top 12 to the top of the economizer diaphragm 110 in the vacuumchamber 112. Below the diaphragm 110 there is a power jet 114 located inthe bottom of the float chamber 18. A valve stem 116 is connected at itsupper end to the diaphragm 110 and its lower end extends through the jet114. A tapered head 118 is secured to the lower end of the stem 116 andthe upper end of the stem is slidably mounted in a plate 120 secured tothe top 12. A coil spring 122 encircles the stem 116 and is compressedbetween the plate 120 and a radial flange on the lower end of the sternso as to normally urge the head away from the restricted openings in thepower jet 114 so as to provide a metered opening therethrough. A lateralpassage 124 communicates the lower portion of the power jet with each ofthe main wells 68.

As engine power demands are reduced, the increased vacuum acting on thediaphragm 110 overcomes the tension of spring 122 and draws theeconomizer diaphragm and stem 116 upwardly thereby closing the power jet114. Conversely, when the accelerator pedal is suddenly depressed, ordepressed at a relatively rapid rate, the manifold pressure increasesthereby increasing the pressure in vacuum chamber 112. This increase inpressure permits the spring 122 to urge the stem 116 downwardly so as toopen the power jet 114 and supply additional fuel to the main wells 68.This additional supply of fuel increases the amount of fuel flowing fromthe nozzles 102 thereby maintaining the fuel-air mixture furnished bythe carburetor at the proper level.

At lower speeds, the secondary throttle plates 36 remain closed,allowing the engine to maintain satisfactory fuel-air velocities anddistribution. When engine speeds increase to a point where additionalbreathing capacity is needed, the secondary throttle plates are openedby the secondary system shown in FIG. 6.

Vacuum taken from one primary venturi 54 is transmitted to the vacuumchamber 42 by means of a short passage 126, an L-shaped passage 128, asloping passage 130 and a short passage 132. At high speeds when enginerequirements approach the capacity of the two primary bores 22 and 24,the strong primary venturi vacuum in the venturis 54 move the diaphragm44 upwardly compression spring 52. The diaphragm 44 acting through therod 46 and plate 45 will commence to open the secondary throttle plates36. The amount which the secondary throttle plates are opened depends onthe strength of the vacuum from the primary venturi 54. This, in' turn,is determined by the air flow through the primary bore to the engine. Asair flow increase through the primary venturies, a greater secondarythrottle plate opening will result and the secondary passages willsupply a larger portion of the engines requirements. As the secondarythrottle plates open, additional vacuum is supplied to the chamber 42 bymeans of a restricted passage 134 extending between one of the secondaryventuris 56 and the passage 126. A ball check valve 136 in passage 130normally rests on a seat having a restricted passage therethrough. Whenthe primary throttles are suddenly opened, vacuum maintains the ballcheck valve 136 on its seat thereby restricting the rate at which air isdrawn from the chamber 42 and thus preventing the secondary valve platesfrom being opened too rapidly.

Fuel is supplied to each of the secondary or high speed passages 26 and28 by a separate system each of which is identical and for simplicity,only one of which is shown in FIG. 6. Each system includes a secondaryjet 138 connected to the top 12 and having a tubular extension 149extending downwardly into the bowl 18. The upper end of the jet 138communicates with a horizontal passage 142 in the top and the outer endof this passage communicates with a diagonal passage 144 in the throttleassembly 16 by means of a vertical exterior pipe 146. The passage 144communicates with a secondary discharge nozzle 148 and secondarytransfer holes 150 in the venturi 56 and passage 26 respectively, bymeans of a passage 152 and check valve 154.

As the secondary throttle plates 36 begin to open, a vacuum is firstcreated at the secondary barrels 26 and 28 and then, as air flowincreases, at the secondary veuturis 56. Fuel is drawn up from the floatchamber 18 through extension 140 and secondary jet 138 passed asecondary air bleed vent where air is admitted to and mixed with thefuel. The secondary air bleed vent 156 also vents the fuel passage 142to prevent a siphoning effect when the secondary system is not inoperation. The fuel and air mixture continues on down the pipe 146,passages 144 and 152 where it is either discharged at the secondarytransfer holes or the secondary discharge nozzle 148 depending on theposition of throttle plate 36. Fuel is first ejected through the holes150, but after the vacuum increases to a suflicient level at the venturi56, the ball check valve 154 is lifted from its seat so as to permitfuel to be supplied to and discharged from the nozzle 148.

When the engine speed is reduced, there is a corresponding reduction invacuum produced at venturies 54 and 56 and in the vacuum chamber 42thereby permitting the spring 52 to gradually close the secondarythrottle plates 36. The secondary throttles 36 are normally opened atspeeds of 45 mph. or above.

The carburetor is also supplied with a conventional accelerating pumpsystem which includes a spring operated pump, not shown, located in ahollow projection 158 on the top 12 and a cylindrical projection 160 onthe main body 14 as illustrated in FIG. 1. The accelerating pumpnormally supplies additional fuel through nozzles 162 at the top of theprimary passages 22 and 24.

As shown in FIG. 1 the throttle linkage is also provided with aconventional dashpot 164 to prevent the primary throttles from closingtoo rapidly.

The above described carburetor is of conventional construction. However,as previously explained, this conventioual carburetor structure hasinherent disadvantages in that it supplies a mixture which is too richduring normal cruising speeds, thereby excessively increasing fuelconsumption and at very high speeds of the engine, the mixture is toolean, thereby reducing the maximum power output of the engine.Accordingly, I propose to improve the conventional carburetor by addingthereto a high speed fuel system as illustrated in FIGS. 2, 4, 7, and 8.This high speed system includes two identical systems, one for each ofthe secondary or high speed passages 26 and 28. Each system includes theaddition of a high speed jet 166 having a threaded upper end 168 whichis threaded through a bore in the top 12. Each jet 166 has an elongatedextension 170 which extends downwardly into the fuel bowl 18. Theextreme upper threaded end of each jet 166 extends through the top 12and is threaded into one end of an L-shaped elbow fitting 172. AnL-shaped tubing 174 is provided for each of the elbow fittings 172. Eachtubing 174 has a horizontal leg 176 extending above the top 12 andhaving one end connected to one elbow fitting by means of a conventionalpipe coupling 178. Each tubing 174 also has a vertical leg 180 whichextends downwardly and terminates within one of the secondary veuturis56. An air bleed orifice 182 is drilled into each elbow fitting directlyon the outside curve of the elbow. This orifice 182 is of such apredetermined diameter so as to prevent any venturi action in thecarburetor from drawing fuel through the high speed jets 166 at all lowand intermediate speeds and the lower end of the high speed range of theengine.

Since the high speed jets 166 supply additional fuel and therebyenrichen the mixture at very high engine speeds, I thereby reduce thesize of the secondary jets 138. Thus, at moderate and intermediatecruising speeds of approximately 45 to 75 mph for example, the secondaryjets 138 being of reduced size, provide a leaner mixture for maximumeconomy. At very high cruising speeds, such as 75 mph. for example, myhigh speed fuel system is designed to operate to supply additional fuelto the secondary passages 26 and 28 and thereby eurichen the mixture toa point where it produces maximum power and also causes the engine tooperate at a cooler temperature thereby prolonging the life of thevalves therein.

The air bleed orifices 182 are substantially larger than the bleedorifices 156 in the secondary fuel system, thereby ensuring that no fuelwill be supplied through the high speed system except at very highspeeds. It is only at very high speeds that the vacuum produced in theventuris 56 is sufficiently great to cause suflicient suction 7 withinthe elbow fitting 172 to suck up fuel through the high speed jets 166from the float chamber 18. Of course, once fuel is sucked up through thehigh speed jets 166, this fuel mixes with air entering through theorifices 182 thereby ensuring that the fuel will be more readilyvaporized once it enters the carburetor and intake manifold. Of course,as the fuel is ejected from the tubing 174 into the secondary venturis56, it mixes with the air entering through opening 58 and this fuel andair mixture passes downwardly Where it is further enrichened by the fuelentering the secondary venturis via the secondary discharge nozzles 148.

It is also contemplated that when maximum fuel economy is desired at lowand intermediate cruising speeds, that the main jets 66 for the mainfuel system shown in FIG. 3 also be removed and replaced by main jets ofa smaller size. Thus, through regulated variations in the size of theorifices 182 in the high speed system, with regulated variations in thesize of the secondary jets 138-140, and even with variations in the sizeof the orifices in the primary jets, a fuel to air ratio can be obtainedthroughout the entire range of speeds from low speed to extremely highspeeds so as to obtain maximum economy and maximum power.

By having the air bleed orifices 182 in the high speed systems, of theproper sizes, use of the high speed jets is prevented when not required,such as during moderate and low cruising speeds, and conversely,automatically permits use of the high speed jets at very high speeds andwide open throttle to supplement the secondary jets when required atvery high speeds, thereby enabling an automatic wide speed rangecarburetion mixture for maximum economy at cruising speeds and maximumpower at very high speeds. Carburetion control as provided by thisinvention is particularly useful for racing vehicles since it permitsthe engines in these vehicles to develop more power at wide openthrottle and very high speeds. Also, the carburetion system provided bythis invention will greatly economize fuel cost during operation ofconventional vehicles.

In summary, a conventional vehicle operating with the carburetor of thisinvention, will operate as follows:

The main or primary jets 66 will supply fuel through a main system atlow speeds such as 30 mph. or above, the secondary jets 138-140 willsupply fuel at intermediate speeds such as 45 mph. and above, the highspeed jets 166 will supply fuel at very high speeds such as 75 m.p.h. orabove, and the power jet 114 will supply fuel as required.

As this invention may be embodied in several forms without departingfrom thespirit or essential characteristics thereof, the presentembodiment is therefore illustrative and not restrictive, since thescope of the invention is defined by the appended claims rather than bythe description preceding them, and all changes that fall within themetes and bounds of the claims or that form their functional as well asconjointly cooperative equivalents, are therefore intended to beembraced by those claims.

What is claimed is:

1. A carburetor comprising a body having air duct means therethroughadapted to be connected to the intake manifold of an internal combustionengine so as to supply and air-fuel mixture from said duct means to saidmanifold, a fuel chamber in said body, first and second venturi means insaid duct means, a main fuel passage from said fuel chamber to saidfirst venturi means, a main fuel metering jet in said main passage, asecondary fuel passage between said second venturi means and said fuelchamber, a secondary fuel metering jet in said secondary passage, saidsecondary fuel passage having an air vent of predetermined size inoperative communication with said secondary fuel metering jetcontrolling the suction thereon and thereby metering the fueltherethrough, an auxiliary passage between said fuel chamber and openinginto said second venturi means, a high speed jet in said auxiliarypassage, said auxiliary passage having an air vent of predetermined sizein operative communication with said high speed jet controlling thesuction thereon and thereby metering the fuel therethrough, said lastmentioned air vent being substantially larger than said first mentionedair vent to prevent venturi action of said second venturi means fromdrawing fuel through the high speed jet at all low and intermediatespeeds of the engine, said main passage adapted to supply fuel to saidfirst venturi means at and above low engine speeds, said secondarypassage adapted to supply fuel to said second venturi means at and aboveintermediate engine speeds, a throttle valve in said duct downstream ofsaid second venturi, pneumatic motor means controlling said throttlevalve, and a fluid control passage connecting said pneumatic motor meansto said first venturi means, whereby when a sufficient vacuum is createdat said first venturi means, during high engine speeds, said throttlevalve will be moved to wide open position thereby creating sufiicientvacuum at said second venturi means to cause said high speed jet tosupply fuel through said auxiliary passage to said second venturi means,and said high speed jet and auxiliary passage at other engine speedsremaining inactive.

2. The carburetor as defined in claim 1, wherein said auxiliary passagehas an angular bend and said air vent opening being in the other side ofsaid angular bend.

References Cited by the Examiner UNITED STATES PATENTS 2,114,970 4/ 1938Rullison et al. 2,208,702 7/ 1940 Read 26169 2,715,522 8/1955 Carlson etal. 26l52 2,890,031 6/1959 Carlson et al. 2614l OTHER REFERENCES 1956Ford Car Shop Manual: Ford Motor Company, Dearborn, Michigan, copyright1955, pages to 100.

HARRY B. THORNTON, Primary Examiner. RONALD R. WEAVER, AssistantExaminer.

1. A CARBURETOR COMPRISING A BODY HAVING AIR DUCT MEANS THERETHROUGHADAPTED TO BE CONNECTED TO THE INTAKE MANIFOLD OF AN INTERNAL COMBUSTIONENGINE SO AS TO SUPPLY AND AIR-FUEL MIXTURE FROM SAID DUCT MEANS TO SAIDMANIFOLD, A FUEL CHAMBER IN SAID BODY, FIRST AND SECOND VENTURI MEANS INSAID DUCT MEANS, A MAIN FUEL PASSAGE FROM SAID FUEL CHAMBER TO SAIDFIRST VENTURI MEANS, A MAIN FUEL METERING JET IN SAID MAIN PASSAGE, ASECONDARY FUEL PASSAGE BETWEEN SAID SECOND VENTURI MEANS AND SAID FUELCHAMBER, A SECONDARY FUEL METERING JET IN SAID SECONDARY PASSAGE, ASECONDARY FUEL PASSAGE HAVING AN AIR VENT OF PREDETERMINED SIZE INOPERATIVE COMMUNICATION WITH SAID SECONDARY FUEL METERING JETCONTROLLING THE SUCTION THEREON AND THEREBY METERING THE FUELTHERETHROUGH, AN AUXILIARY PASSAGE BETWEEN SAID FUEL CHAMBER AND OPENINGINTO SAID SECOND VENTURI MEANS, A HIGH SPEED JET IN SAID AUXILIARYPASSAGE, SAID AUXILIARY PASSAGE HAVING AN AIR VENT OF PREDETERMINED SIZEIN OPERATIVE COMMUNICATION WITH SAID HIGH SPEED JET CONTROLLING THESUCTION THEREON AND THEREBY METERING THE FUEL THERETHROUGH, SAID LASTMENTIONED AIR VENT BEING SUBSTANTIALLY LARGER THAN SAID FIRST MENTIONEDAIR VENT TO PREVENT VENTURI ACTION OF SAID SECOND VENTURI MEANS FROMDRAWING FUEL THROUGH THE HIGH SPEED JET AT ALL LOW AND INTERMEDIATESPEEDS OF THE ENGINE, SAID MAIN PASSAGE ADAPTED TO SUPPLY FUEL TO SAIDFIRST VENTURI MEANS AT AND ABOVE LOW ENGINE SPEEDS, SAID SECONDARYPASSAGE ADAPTED TO SUPPLY FUEL TO SAID SECOND VENTURI MEANS AT AND ABOVEINTERMEDIATE ENGINE SPEEDS, A THROTTLE VALVE IN SAID DUCT DOWNSTREAM OFSAID SECOND VENTURI, PNEUMATIC MOTOR MEANS CONTROLLING SAID THROTTLEVALVE, AND A FLUID CONTROL PASSAGE CONNECTING SAID PNEUMATIC MOTOR MEANSTO SAID FIRST VENTURI MEANS, WHEREBY WHEN A SUFFICIENT VACUUM IS CREATEDAT SAID FIRST VENTURI MEANS, DURING HIGH ENGINE SPEEDS, SAID THROTTLEVALVE WILL BE MOVED TO WIDE OPEN POSITION THEREBY CREATING SUFFICIENTVACUUM AT SAID SECOND VENTURI MEANS TO CAUSE SAID HIGH SPEED JET TOSUPPLY FUEL THROUGH SAID AUXILIARY PASSAGE TO SAID SECOND VENTURI MEANS,AND SAID HIGH SPEED JET AND AUXILIARY PASSAGE AT OTHER ENGINE SPEEDSREMAINING INACTIVE.